drivers/platform/surface/aggregator/ssh_msgb.h

   1 /* SPDX-License-Identifier: GPL-2.0+ */
   2 /*
   3  * SSH message builder functions.
   4  *
   5  * Copyright (C) 2019-2022 Maximilian Luz <luzmaximilian@gmail.com>
   6  */
   7
   8 #ifndef _SURFACE_AGGREGATOR_SSH_MSGB_H
   9 #define _SURFACE_AGGREGATOR_SSH_MSGB_H
  10
  11 #include <linux/unaligned.h>
  12 #include <linux/types.h>
  13
  14 #include <linux/surface_aggregator/controller.h>
  15 #include <linux/surface_aggregator/serial_hub.h>
  16
  17 /**
  18  * struct msgbuf - Buffer struct to construct SSH messages.
  19  * @begin: Pointer to the beginning of the allocated buffer space.
  20  * @end:   Pointer to the end (one past last element) of the allocated buffer
  21  *         space.
  22  * @ptr:   Pointer to the first free element in the buffer.
  23  */
  24 struct msgbuf {
  25         u8 *begin;
  26         u8 *end;
  27         u8 *ptr;
  28 };
  29
  30 /**
  31  * msgb_init() - Initialize the given message buffer struct.
  32  * @msgb: The buffer struct to initialize
  33  * @ptr:  Pointer to the underlying memory by which the buffer will be backed.
  34  * @cap:  Size of the underlying memory.
  35  *
  36  * Initialize the given message buffer struct using the provided memory as
  37  * backing.
  38  */
  39 static inline void msgb_init(struct msgbuf *msgb, u8 *ptr, size_t cap)
  40 {
  41         msgb->begin = ptr;
  42         msgb->end = ptr + cap;
  43         msgb->ptr = ptr;
  44 }
  45
  46 /**
  47  * msgb_bytes_used() - Return the current number of bytes used in the buffer.
  48  * @msgb: The message buffer.
  49  */
  50 static inline size_t msgb_bytes_used(const struct msgbuf *msgb)
  51 {
  52         return msgb->ptr - msgb->begin;
  53 }
  54
  55 static inline void __msgb_push_u8(struct msgbuf *msgb, u8 value)
  56 {
  57         *msgb->ptr = value;
  58         msgb->ptr += sizeof(u8);
  59 }
  60
  61 static inline void __msgb_push_u16(struct msgbuf *msgb, u16 value)
  62 {
  63         put_unaligned_le16(value, msgb->ptr);
  64         msgb->ptr += sizeof(u16);
  65 }
  66
  67 /**
  68  * msgb_push_u16() - Push a u16 value to the buffer.
  69  * @msgb:  The message buffer.
  70  * @value: The value to push to the buffer.
  71  */
  72 static inline void msgb_push_u16(struct msgbuf *msgb, u16 value)
  73 {
  74         if (WARN_ON(msgb->ptr + sizeof(u16) > msgb->end))
  75                 return;
  76
  77         __msgb_push_u16(msgb, value);
  78 }
  79
  80 /**
  81  * msgb_push_syn() - Push SSH SYN bytes to the buffer.
  82  * @msgb: The message buffer.
  83  */
  84 static inline void msgb_push_syn(struct msgbuf *msgb)
  85 {
  86         msgb_push_u16(msgb, SSH_MSG_SYN);
  87 }
  88
  89 /**
  90  * msgb_push_buf() - Push raw data to the buffer.
  91  * @msgb: The message buffer.
  92  * @buf:  The data to push to the buffer.
  93  * @len:  The length of the data to push to the buffer.
  94  */
  95 static inline void msgb_push_buf(struct msgbuf *msgb, const u8 *buf, size_t len)
  96 {
  97         msgb->ptr = memcpy(msgb->ptr, buf, len) + len;
  98 }
  99
 100 /**
 101  * msgb_push_crc() - Compute CRC and push it to the buffer.
 102  * @msgb: The message buffer.
 103  * @buf:  The data for which the CRC should be computed.
 104  * @len:  The length of the data for which the CRC should be computed.
 105  */
 106 static inline void msgb_push_crc(struct msgbuf *msgb, const u8 *buf, size_t len)
 107 {
 108         msgb_push_u16(msgb, ssh_crc(buf, len));
 109 }
 110
 111 /**
 112  * msgb_push_frame() - Push a SSH message frame header to the buffer.
 113  * @msgb: The message buffer
 114  * @ty:   The type of the frame.
 115  * @len:  The length of the payload of the frame.
 116  * @seq:  The sequence ID of the frame/packet.
 117  */
 118 static inline void msgb_push_frame(struct msgbuf *msgb, u8 ty, u16 len, u8 seq)
 119 {
 120         u8 *const begin = msgb->ptr;
 121
 122         if (WARN_ON(msgb->ptr + sizeof(struct ssh_frame) > msgb->end))
 123                 return;
 124
 125         __msgb_push_u8(msgb, ty);       /* Frame type. */
 126         __msgb_push_u16(msgb, len);     /* Frame payload length. */
 127         __msgb_push_u8(msgb, seq);      /* Frame sequence ID. */
 128
 129         msgb_push_crc(msgb, begin, msgb->ptr - begin);
 130 }
 131
 132 /**
 133  * msgb_push_ack() - Push a SSH ACK frame to the buffer.
 134  * @msgb: The message buffer
 135  * @seq:  The sequence ID of the frame/packet to be ACKed.
 136  */
 137 static inline void msgb_push_ack(struct msgbuf *msgb, u8 seq)
 138 {
 139         /* SYN. */
 140         msgb_push_syn(msgb);
 141
 142         /* ACK-type frame + CRC. */
 143         msgb_push_frame(msgb, SSH_FRAME_TYPE_ACK, 0x00, seq);
 144
 145         /* Payload CRC (ACK-type frames do not have a payload). */
 146         msgb_push_crc(msgb, msgb->ptr, 0);
 147 }
 148
 149 /**
 150  * msgb_push_nak() - Push a SSH NAK frame to the buffer.
 151  * @msgb: The message buffer
 152  */
 153 static inline void msgb_push_nak(struct msgbuf *msgb)
 154 {
 155         /* SYN. */
 156         msgb_push_syn(msgb);
 157
 158         /* NAK-type frame + CRC. */
 159         msgb_push_frame(msgb, SSH_FRAME_TYPE_NAK, 0x00, 0x00);
 160
 161         /* Payload CRC (ACK-type frames do not have a payload). */
 162         msgb_push_crc(msgb, msgb->ptr, 0);
 163 }
 164
 165 /**
 166  * msgb_push_cmd() - Push a SSH command frame with payload to the buffer.
 167  * @msgb: The message buffer.
 168  * @seq:  The sequence ID (SEQ) of the frame/packet.
 169  * @rqid: The request ID (RQID) of the request contained in the frame.
 170  * @rqst: The request to wrap in the frame.
 171  */
 172 static inline void msgb_push_cmd(struct msgbuf *msgb, u8 seq, u16 rqid,
 173                                  const struct ssam_request *rqst)
 174 {
 175         const u8 type = SSH_FRAME_TYPE_DATA_SEQ;
 176         u8 *cmd;
 177
 178         /* SYN. */
 179         msgb_push_syn(msgb);
 180
 181         /* Command frame + CRC. */
 182         msgb_push_frame(msgb, type, sizeof(struct ssh_command) + rqst->length, seq);
 183
 184         /* Frame payload: Command struct + payload. */
 185         if (WARN_ON(msgb->ptr + sizeof(struct ssh_command) > msgb->end))
 186                 return;
 187
 188         cmd = msgb->ptr;
 189
 190         __msgb_push_u8(msgb, SSH_PLD_TYPE_CMD);         /* Payload type. */
 191         __msgb_push_u8(msgb, rqst->target_category);    /* Target category. */
 192         __msgb_push_u8(msgb, rqst->target_id);          /* Target ID. */
 193         __msgb_push_u8(msgb, SSAM_SSH_TID_HOST);        /* Source ID. */
 194         __msgb_push_u8(msgb, rqst->instance_id);        /* Instance ID. */
 195         __msgb_push_u16(msgb, rqid);                    /* Request ID. */
 196         __msgb_push_u8(msgb, rqst->command_id);         /* Command ID. */
 197
 198         /* Command payload. */
 199         msgb_push_buf(msgb, rqst->payload, rqst->length);
 200
 201         /* CRC for command struct + payload. */
 202         msgb_push_crc(msgb, cmd, msgb->ptr - cmd);
 203 }
 204
 205 #endif /* _SURFACE_AGGREGATOR_SSH_MSGB_H */